Touching of a capacitive sensor or approaching a capacitive proximity sensor by an object, e.g., a piece of metal, a finger, a hand, a foot, a leg, etc., changes certain parameters thereof, in particular the capacitance value of a capacitor that is built into the touch sensor used, for example, in human to machine interface devices, e.g., keypad or keyboard. Microcontrollers now include peripherals that enhance the detection and evaluation of such capacitive sensors. One such application utilizes capacitive voltage division (CVD) to evaluate whether a capacitive touch element has been touched or not. Another application utilizes a charge time measurement unit (CTMU) to charge a capacitive touch element with a constant current source over a precise time, then measuring a resulting voltage on the capacitive touch element at the end of the precise time. Still another application is measuring a change in frequency by a capacitive sensing module (CSM) that is proportional to a change in the capacitance of the capacitive touch element. However, when such sensors are operated in high noise environments, the resolution or detection in conventional systems may not suffice.
In particular parasitic capacitance may pose a problem in many capacitive sensor applications. Parasitic capacitance is generated whenever a conductor adjacent to the sensor (or its connection to the microcontroller) is at a different voltage potential then the sensor. Therefore it is preferable to reduce the parasitic capacitance associated with capacitive sensors, assuming that parasitic capacitance may decrease the sensitivity of a capacitive sensor and thereby decrease the resolution of the resulting capacitive conversion process, e.g., CVD, CTMU or CSM.